1. Field of the Invention
This invention relates to a process for continuously producing tertiary butyl alcohol (referred to hereinafter as TBA) from isobutylene and water using tertiary butyl alcohol as a solvent in the presence of a cation exchange resin in a series multistage reactor.
2. Description of the Background
Many methods for producing TBA by hydration reaction from isobutylene and water using an ion exchange resin catalyst have been known. Known are, for example, a method in which an organic acid is used as a solvent (JP-B-53-20,482, JP-B-53-14,044 and JP-B-56-22,855), a method in which a polar solvent is used (JP-A-56-34,643, JP-A-57-108,028, JP-A-56-87,526, JP-B-57-10,853, JP-A-56-10,124 and JP-A-60-233,024), a method in which TBA is used as a polar solvent (JP-B-57-10,853, JP-A-56-10,124 and JP-A-60-233,024) and a method in which the reaction is effected in a heterogeneous system without using a solvent (JP-A-54-27,507, JP-A-54-30,104, JP-A-54-30,105, JP-A-55-85,529 and JP-A-55-108,825).
However, the method in which an organic acid is used as a solvent has such problems that the TBA produced is reacted with the organic acid, which is the solvent, to produce a large amount of an organic acid ester as a by-product, so that the utilization of the starting materials is lowered and that in order to increase the utilization, an operation for hydrolyzing the organic acid ester produced as a by-product becomes necessary. In addition, there is also a problem that the method requires an expensive apparatus material resistant to corrosion with the organic acid used as the solvent.
The method in which other polar solvents than TBA are used can increase the yield by a combination of the solvent used with a reaction process; however, there are such problems that incidental facilities become necessary for separating TBA from the polar solvent and hence the equipment cost is increased.
In the method in which TBA is used as the solvent, the catalyst cannot be effectively utilized because the reaction liquid composed of the starting C.sub.4 mixture, water and TBA forms a heterogeneous phase in the vicinity of the reactor inlet. Therefore, such measures have been taken that a large amount of TBA is added to the reaction system so that the reaction liquid forms a homogeneous phase and that a decanter and a distillation column are placed between plural reaction vessels. However, all the measures have such a problem that the service cost or the equipment cost becomes high. Moreover, a method in which the reaction is effected using a piston type reactor has been considered, but the reaction liquid is heterogeneous in the inlet portion of the reactor, so that the reaction does not proceed and it follows that the hydration reaction is accelerated by elevating the reaction temperature. Therefore, there is a problem that the amounts of isobutylene dimer, secondary butyl alcohol and the like produced as by-products are increased.
The method in which the reaction is effected in a heterogeneous system without using a solvent or the like is low in reaction rate, and hence, requires a larger reactor than other methods in order to secure the necessary production. Accordingly, when the method is carried out on a commercial scale, there is a problem that the equipment cost becomes high. Moreover, the above method has also a problem in that the amounts of isobutylene dimer or secondary butyl alcohol produced as by-products become large.
Since TBA is used as the starting material for producing methyl methacrylate by a gas phase catalytic oxidation or producing high purity isobutylene; as a gasoline additive; or the like, it is desirable that the amounts of isobutylene dimer, secondary butyl alcohol and the like produced as by-products are as small as possible.